I proposed a similar approach in this forum a few years ago, to include a badge that would distinguish longer logs with higher variation content, i.e. individual logs. However, this was rejected with the argument in nuce that such a ranking would vary over time and also go down as soon as the user starts writing shorter logs again or using standard phrases. Such argument is weak, however, as it could then equally be applied to existing badges such as log length, which after all can fluctuate just as much over time.